The guy in the video is taking some awful chances. He's pushing down on the crank, whch is inviting a kickback, and a broken wrist, or jaw, or worse. The right way to hand-crank any engine is to position the crank handle at the bottom, grasp the handle with all your fingers, including your thumb, on the same side, and make a quick 1/2 turn pull, stopping at the top. If the engine kicks back, the crank handle will straighten out your fingers without creating any injuries. Just get your wrist out of the way before the handle swings around and breaks something! A well-tuned engine should start with one or two pulls. If it's cold, pull it a time or two with the ignition turned off, and the choke pulled. Be careful not to flood the engine!
Jerry
